The invention relates to a pipe sealing apparatus that is insertable in pipelines of varying diameters and inflatable therein to seal a section of pipeline. Such a pipe sealing apparatus is commonly referred to as an inflatable plug assembly.
Inflatable plugs provide a useful means to mitigate the uncontrolled release of fluids from a pipeline when a break occurs in the pipeline and can also be used to isolate sections of pipeline when performing repair or maintenance on the pipeline.
One prior art inflatable plug is described in U.S. Pat. No. 5,901,752 which is assigned to the assignee of the present invention. The inflatable plug described there includes a first support member disposed at a first end and a second support member disposed at a second end. The inflatable plug includes an elongated inflatable sleeve of elastomeric material. The inflatable sleeve has a first sleeve end sealingly engaging the first support member to form a first ring of folds wrapped around the first support member when viewed in cross section generally perpendicular to a longitudinal axis of the first support member, and a second sleeve end sealingly engaging the second support member to form a second ring of folds wrapped around the second support member when viewed in cross section generally perpendicular to a longitudinal axis of the second support member. An inner surface of the inflatable sleeve extends between the first and second inflatable sleeve ends and substantially defines an expandable inflatable space therein. A fluid supply inlet is disposed at the first end of the apparatus. The inlet is positioned in fluid communication with the inflatable space and operable to deliver fluid into the inflatable space to inflate the inflatable space. The apparatus further includes an elongated outer sleeve that substantially surrounds the inflatable sleeve and has an inner surface. The outer surface of the inflatable space is shiftable with respect to the inner surface of the outer sleeve during inflation of the inflatable space. The outer sleeve has a first sleeve end sealingly engaged around the first ring of folds to form a third ring of folds and a second outer sleeve end sealingly engaged around the second ring of folds to form a fourth ring of folds. The third and fourth ring of folds are positioned radially outward from the first and second ring of folds respectively.
Another inflatable plug is described in U.S. Pat. No. 4,565,222, also assigned to the assignee of the present invention. The inflatable plug described there includes an inflatable plug of flexible sheet material that is constructed to form an elongated cylinder. The ends of the inflatable plug are wrapped around rigid end supports and then metal collars are placed over the ends of the inflatable plug. The metal collars are swaged or clamped down to form a fluid tight seal between the end supports and the collars. One of the rigid end supports includes an open pipe connectable to a pressurized air or water supply. The plug is inserted into the pipeline in the deflated state and maneuvered into the desired section of the pipeline. Pressurized air or water is then delivered through the open pipe to fill the inflatable plug. The inflatable plug expands to fill the pipeline section and frictionally engages the inside wall of the pipeline section, thereby sealing or plugging the pipeline.
Another prior art inflatable plug may be used to clear a blockage inside a pipeline as well as to seal the pipeline. Such an inflatable plug is commonly referred to as a flow-through type inflatable plug. An example of a flow-through inflatable plug is described in U.S. Pat. No. 5,353,842, which is also assigned to the assignee of the present invention. The inflatable plug shown there includes an elongated cylinder with a central, longitudinal bore and an expandable covering surrounding the central cylinder. The expandable covering is comprised of an elastomeric material which is wrapped around the cylinder. At one end of the inflatable plug, a first fluid inlet is provided for delivering pressurized air or water between the outer surface of the cylinder and the inner surface of the covering and a second fluid inlet is provided for delivering pressurized fluid to the cylinder bore. When the plug is inserted in a pipeline adjacent a pipe blockage, the first fluid inlet is used to inflate and expand the space between the covering and the cylinder, such that the outer surface of the plug sealingly engages the inside surface of the pipeline section. Then, pressurized fluid is delivered through the second fluid inlet and into the cylinder bore. This pressurized fluid is discharged at the opposite end of the cylinder bore in the direction of the pipe blockage, thereby clearing the blockage from the pipe.
The present invention provides an inflatable plug assembly that includes a first inflatable plug connected to a second inflatable plug by an elongated flexible tensile member and a fluid pressure hose. Each inflatable plug has a plurality of ports that may be connected to a fluid pressure source, plugged, or left unplugged depending upon the application. The second inflatable plug may be inflated either simultaneously with the first plug, or independently of the first plug. Each inflatable plug also has a fluid flow-through conduit.
The invention also provides a method for sealing a defined section of pipe. A first inflatable plug and a second inflatable plug are positioned in a spaced apart relation in a section of pipe, the first and second inflatable plugs being connected by an elongated flexible tensile member and by a fluid pressure hose. The fluid pressure hose may be connected for either common inflation or independent inflation. Once the inflatable plug assembly is positioned in the desired spaced apart relation in the pipe, the plugs are inflated by connecting the first inflatable plug to a fluid pressure source. When the inflatable plug assembly has sealed the defined section of pipeline, the operator may then proceed to perform the desired function.
The invention also provides a method for evacuating a defined section of pipe. After the section of pipeline has been sealed using a first and second inflatable plug connected for common inflation, the isolated area can be evacuated for repair or maintenance. In order to completely evacuate the isolated area, a hose can be attached to the fluid flow-through conduit of the first inflatable plug. The opposite end of the fluid flow-through conduit of the first plug is attached to a hose that is connected to a pump for removal of material located in the isolated area. The fluid flow-through conduit of the second plug is capped to seal the isolated area. The fluid is pumped from the isolated area until all material has been evacuated. The operator may then perform the desired repair or maintenance on the section of pipeline. When replacing a valve in the pipeline, for example, a plug assembly may be inserted into the pipeline such that it is positioned both upstream and downstream of the valve to thereby isolate the valve from the pipeline system and to allow for removal of the old valve. Inflatable plug assemblies may also be used with existing pipeline valves to safely isolate an area where hot work is to be performed.
The invention also provides a method for pressure testing a defined section of pipe. After a section of pipeline has been sealed using a first and second inflatable plug connected for common inflation, the isolated area can be pressure tested. The flow-through conduit of the first plug is set up similar to the evacuation process with the exception of the pump forcing fluid into the isolated area instead of removing it from the isolated area. A pressure testing device is connected to the independent inflation conduit which is in fluid communication with the isolated area. As the pump fills the isolated area with pressurized fluid, the pressure testing device produces an output indicating the pressure in the area. The operator can fill the isolated area to whatever pressure is needed to assure the segment of pipeline retains the ability to withstand predetermined pressure levels.
The invention also provides a method for fluid flow through a defined section of pipeline. After the section of pipeline has been sealed using a first and second inflatable plug connected for either common inflation or independent inflation, the fluid can flow through the inflatable plug assembly until the broken pipe segment is repaired or replaced. The flow-through conduit of the first plug is connected to the flow-through conduit of the second plug by connecting a flexible hose to the threaded interior ends of the first and second plugs. The threaded exterior ends are also left open to allow fluid to flow freely through the assembly. The fluid ports that are not used are plugged.
The invention also provides a method for plugging a pipeline wherein multiple plugs are used in series to present a greater friction force in opposition to the pressure in the pipeline. The inflatable plugs are used in series and the multiple plugs are set up for common inflation.